An extrusion blow molded component made of thermoplastic having a blind hole provided in the wall thereof, which blind hole is provided with a thread, is known, for example, from published German patent application DE 2 453 060. DE 2 453 060 describes a method of producing a connecting piece open on both sides and provided with an internal thread in a flat or curved plastics wall deformable in the thermoplastic state. A plug piece is provided with an internal thread and threads projecting into the interior of a plastics container are produced using an expandable mold core when shaping the container. In this case, to form an internally threaded connecting piece initially open on one side, the mold core is pressed, with lengthwise movement, perpendicularly into the thermoplastically deformable plastics wall. Once the threaded connecting piece has been shaped as a blind hole, the radially stressed, disc-shaped base part of the connecting piece is pierced. Finally, the mold core is removed once the plastic has solidified. In this way, a connecting piece with an internal thread shaped during blow molding is simply produced for an extrusion blow molded plastics container.
When producing extrusion blow molded components, in particular when producing containers, it is in principle also known to provide threads therein by encapsulating inserts by blow molding.
A method is known from German patent 1 251 009 for producing a hollow body provided with a threaded bushing from a thermoplastic, in which method a parison is expanded in a manner known per se inside a mold cavity. Upon expansion of the parison, the threaded bushing is enclosed thereby and blow molded therein.
In this way, an extrusion blow molded component is obtained, whose outer wall is configured for mounting a fastening element cooperating with the thread. The threaded bushing enclosed by the component allows simple mounting of fastening elements provided with a matching thread.
The above-described method is relatively complex, insofar as a threaded bushing has to be provided as a component to be produced in a separate operation. For example, such a threaded bushing may be produced by injection molding from a material which is weldable to the container wall. For fastening components undetachably to the container wall, encapsulation of threaded bushings by blow molding tends to be less advantageous. If industrial components need to be produced with a plurality of fastening points, this cannot be achieved by means of the above-described method without excessive effort.